Cristiano Casucci

Effects of organic amendment and herbicide treatment on soil microbial biomass

Abstract The interactive effects of vermi-compost from sewage sludge and either the sulfonylurea herbicide, rimsulfuron, or the imidazolinone herbicide, imazethapyr, on some soil biochemical and microbiological properties were investigated. The herbicides were applied at field and 10-fold field rates. Both herbicides exerted a detrimental effect on soil microbial biomass and its biochemical properties. Even though the effect of both herbicides on soil microbial biomass was not detectable at the field rate, some significant influences on acid and alkaline phosphatase were observed. The higher rate of herbicide application impaired the observed microbial parameters to a greater degree. The detrimental effects seemed to be reduced by organic amendments. Among the studied microbial characteristics, the specific respiration quotient was particularly reliable and sensitive in determining the influence of herbicides on the soil microbial biomass. In this paper a new synthetic index, specific hydrolytic activity (qFDA), for assessing microbial activity in reply to xenobiotic treatments is proposed.

The effect of initial concentration, co-application and repeated applications on pesticide degradation in a biobed mixture

A 180 d laboratory experiment was conducted to investigate the degradation rates of chlorpyrifos (10 and 50 mg kg(-1)) and metalaxyl (100 mg kg(-1)) separately and co-applied in a biomix constituted by topsoil, vine-branches and urban-waste-garden compost. The effect of repeated application of metalaxyl was also investigated. Microbial biomass-C (MBC) content and metabolic quotient (qCO(2)) were measured to evaluate changes in microbial biomass size and activity induced by the presence of the two pesticides. Degradation rate decreased with increasing concentration of chlorpyrifos in all treatments. Metalaxyl half-life was significantly reduced in co-application with chlorpyrifos indicating a synergic interaction between the two pesticides in favour of enhanced degradation rate for metalaxyl but not for chlorpyrifos. Furthermore, repeated application resulted in a sharp reduction of metalaxyl half-life from 37 d after first application to 4 d after third application. MBC content was negatively influenced by the addition of pesticides but it started to recover immediately, in both separate and co-applied treatments, reaching the control value when pesticide residues were about 50% of the initial concentration. The qCO(2) reached a steady-state after about 20 d in separately applied and 40 d in co-applied treatments, indicating a tendency to arrive at a new metabolic equilibrium. In conclusion, the biomix tested has been shown to degrade pesticides relatively fast and to have a microbial community that is varied enough to allow selection of those microorganisms able to degrade metalaxyl and chlorpyrifos.

Fungicides degradation in an organic biomixture: impact on microbial diversity

Biological systems are being developed all over EU countries to protect water-bodies from pesticide contamination at farm level. A laboratory experiment was carried out to test the efficiency of a mixture of compost and straw in bio-degrading different mixtures of fungicides usually applied in vineyards. At the same time the effects of fungicide applications on microbial community of biomixture were also evaluated. Results showed that the biomixture had a good capability of degrading pesticides. Indeed, at the end of the experiment (112 days), the concentration of most of the pesticides was close to complete degradation. Denaturing gradient gel electrophoresis (DGGE) analysis showed an evident modification of microbial diversity after the addition of fungicides. However, at the end of degradation process, no significant changes in the composition of microbial community were seen. In this specific substrate used in the biomixture, yeast flora and ascomycete filamentous fungi seemed to be involved in the degradation activity.

Effectiveness of microbial indexes in discriminating interactive effects of tillage and crop rotations in a Vertic ustorthens

Abstract. Conservation tillage is a soil management practice able to reduce erosion, increase organic matter content and improve physical, chemical and biological soil properties. Conservation tillage reduces the incorporation of crop residues into the soil profile and minimises the exposure of humified organic matter to biotic and abiotic degradative processes. In this article the effect of conventional (ploughing at 40-cm depth coupled with harrowing at 20-cm depth) and reduced tillage (harrowing at 20-cm depth) and two rotations (vetch-oat/wheat and fallow/wheat) on biochemical and microbial properties of a Vertic Ustorthens, located in a semi-arid region of southern Italy, has been investigated. Tillage had a more pronounced effect on soil properties studied here than did rotations. By comparison to conventional tillage (CT), the reduced tillage (RT) resulted in improved soil C and microbial biomass content. Even though some of the selected enzymes showed seasonal variability and, when averaged across the sampling period, were not always able to discriminate among treatments, their sum showed a strong correlation with soil organic C and soil microbial biomass C (MBC), for all these parameters increased in RT plots.

Retention capacity of an organic bio-mixture against different mixtures of fungicides used in vineyards.

A laboratory experiment was carried out to test the efficiency of a bio-mixture made up of pruning residues at two (PR2) and five (PR5) years of composting and wheat straw (STW) in the biological cleaning of water contaminated by different mixtures of fungicides usually employed in vineyards. The experiment was conducted and reproduced at a scale of 1:100 of operating field conditions. Commercial formulates of penconazole (PC), (RS)-1-[2-(2,4-dichlorophenyl)pentyl]-1H-1,2,4-triazole), dimetomorph (DM), (EZ)-4-[3-(4-chlorophenyl)-3-(3,4-dimethoxyphenyl)acryloyl]morpholine), azoxystrobin (AZ), (methyl (E)-2-{2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl}-3-methoxyacrylate), iprovalicarb (IP), (isopropyl 2-methyl-1-[(RS)-1-p-tolylethyl]carbamoyl-(S)-propylcarbamate), metalaxyl (MX), (methyl N-(methoxyacetyl)-N-(2,6-xylyl)-DL-alaninate), fludioxonil (FL), (4-(2,2-difluoro-1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile) and cyprodinil (CY), (4-cyclopropyl-6-methyl-N-phenylpyrimidin-2-amine) were mixed in water and discharged into the bio-mixture following the time schedule of the treatments carried out in the grapevine in real field conditions. At each treatment, contaminated water with fungicides was circulated repeatedly through the bio-mixture to enhance the sorption of fungicides. In fact, it retained them between 98–100% with the exception of MX of which it was able to retain only 90.5%. The adsorption/desorption experiment showed that repeated circulation of water, instead of enhancing MX retention, can easily remove about 30% of MX already adsorbed by the bio-mixture. This finding suggests that water contaminated by very mobile pesticides should be discharged at the end of field treatments without re-circulating the water in order to avoid the release of pesticides weakly adsorbed on the bio-mixture.

Biochemical parameter changes in urban-waste compost used as biofilter for pesticide decontamination

Urban-waste compost (UWC) can be used as a biofilter filling to reduce the effects of pesticide spills. Here, water that was contaminated by three different pesticides, the insecticide chlorpyrifos (Chl), the fungicide metalaxyl (Meta) and the herbicide glyphosate (Gly), was percolated through 2 kg of UWC material. The pesticide residues in the leached water and the modifications induced in some of the UWC biochemical and microbiological parameters (including microbial biomass carbon (MBC) and nitrogen (MBN), and fluorescein diacetate (FDA) hydrolysis, alkaline monophosphatase (AMP) and dehydrogenase (DH) activities) were investigated over 2 months of incubation at 20°C. The UWC showed a good retention capacity towards the three pesticides tested, with the highest efficiency for Gly. Chl caused an initial detrimental effect on the MBC content and a decrease in the FDA hydrolysis capacity, while Meta and Gly increased the MBC content throughout the incubation. The results demonstrate that UWC can be successfully used as a biofilter to reduce pesticide spills and to clean up water contaminated with pesticides. The evaluation of the modifications induced on the UWC MBC and MBN, and FDA hydrolysis, AMP and DH activities suggest different biodegradation potentials of the UWC micro-organisms vs. the three pesticides studied.

Moist olive husks addition to a silty clay soil: influence on microbial and biochemical parameters.

To investigate the effects of moist olive husks (MOH-residues) on soil respiration, microbial biomass, and enzymatic (o-diphenoloxidase, β-glucosidase, dehydrogenase and alkaline phosphatase) activities, a silty clay soil was incubated with 0 (control), 8 × 103 (D), 16 × 103 (2D) and 80 × 103 (10D) kg ha−1 of MOH-residues on a dry weight basis. Soil respiration and microbial biomass data indicated that the addition of MOH-residues strongly increased microbial activity proportionally to the amounts added. Data of qCO2 suggested that the respiration to biomass ratio of the microbial population was strongly modified by MOH-residues additions during the first 90 days of incubation. The qCO2 data suggested a low efficiency in energy yields from C oxidation during the first 2 months of soil incubation. qFDA seemed to be relatively unaffected for treatments D and 2D as compared to the control, but was significantly lowered by the application of 10D, showing the lowest hydrolytic activity of microbial biomass in this treatment up to 360 days of incubation. o-Diphenoloxidase activity was delayed, and this delay was extended with the addition of larger quantities of MOH-residues. Alkaline phosphatase, β-glucosidase and dehydrogenase activities were in line with the findings on microbial biomass changes and activities. The biological and biochemical data suggest that the addition of a large quantity of MOH-residues (80 × 103 kg ha−1) strongly modifies the soil characteristics affecting the r- and K-strategist populations, and that these changes last for at least the 360 days of incubation. The data also suggest that application rates exceeding 16 × 103 kg ha−1 are not recommended until the agro-chemical and -physical functions of the soil are further studied.

Evaluation of BiomassBed system in bio-cleaning water contaminated by fungicides applied in vineyard

BiomassBed is an indirect system designed to collect accidental pesticide spills as well as water remnants of tank sprayers. This system was installed in a vineyard and tested in bio-cleaning water that was contaminated by fungicides in a two-year-field experiment. At the end of each treatment, wastewater of sprayer tanks containing mixtures of cymoxanil, dimethomorph, metalaxyl M, folpet, penconazole, cyprodinil, fludioxonil, azoxystrobin, mandipropamid, pyraclostrobin at different concentrations were discharged into the BiomassBed and repeatedly circulated through an organic biofilter of pruning residues and straw for fungicide adsorption and biodegradation. Water collected was sampled and analysed for fungicide residues, and organic biofilter was analysed to assess fungicide dissipation. Fungicides were removed from water in a range of 92.4–100% of the initial concentration. Metalaxyl M was the least retained and probably desorbed during recirculation of water. However, metalaxyl M residues dissipated ...

Losses and dissipation of penconazole in vineyard soil as affected by mid-row management system

A field experiment was performed with the aim to assess the amount of penconazole losses during field application and the spatial variability of penconazole concentration in a vineyard soil, under two different management techniques (tilled and grass covered). The field dissipation of penconazole under the two techniques was also followed for 114 days, highlighting the effects of spatial variability of the initial concentration and of the grass covering in terms of the different soil metabolic activity. Data found show that a high percentage of penconazole, from 42.5 % to 67.43 %, can reach the soil during the treatments, despite the fact that penconazole is applied to the foliage. The high values of the coefficient of variation for data within rows show considerable variability in all applications, ranging from 30 to 65 in the first application, from 35 to 79 in the second and from 36 to 75 in the third. Since the applications of penconazole occurred under almost same climatic conditions in terms of wind speed and direction, the high variability of concentration of penconazole found within mid-rows was attributed to the uneven slope of the vineyard causing an irregular speed of the sprayer equipment. However, least significant differences of the mean values did not end in a significant difference of penconazole concentration among mid-rows for all applications, indicating that the variability between rows does not contribute to the overall variability. The calculated half-life values for penconazole in tilled soil were 62.4 days for tilled and 33.0 for grassed soil, highlighting the tendency of penconazole to faster dissipate in grassed than in tilled soil. Grassed soil was characterised by a higher metabolic activity in terms of microbial biomass carbon content, basal respiration and total hydrolytic activity, than tilled soil. A significant correlation between penconazole dissipation and total hydrolytic activity, was found. The faster dissipation of penconazole in grassed soil was attributed to the higher amount of the total hydrolytic activity which, in grassed soil, was 1.5 fold-higher than in tilled soil.